/**
 * 新建一个0到99的数组
 */
// ES6, 可以从类数组获取元素,形如 {length: 10} Array.from
let a = new Array(100);
let b = Array.from(a.keys());
// console.log(b);
// let c = { length: 10 };
// console.log(Array.from(c));
